1. Field of the invention
The present invention is generally concerned with friction disks of the type used in clutches, for automobile vehicles in particular.
2. Description of the prior art
As is known, a friction disk of this kind comprises, at its periphery, two annular friction facing members disposed on respective sides of support vanes which are appropriately distributed in the circumferential direction and each of which is coupled axially to each of said support vanes, whether such support vanes are in one piece with a flange carried by a hub or each is individually attached to a flange of this kind.
The present invention is more particularly directed to those friction disks of this kind which, adapted to provide for progressive engagement of the clutches of which they form part, are commonly described as progressively acting.
Such progressively acting friction disks are described, for example, in French Pat. No. 2,094,693 filed Jan. 10, 1970 under the No. 70 24132 and in U.S. Pat. No. 2,256,698.
In both cases the required progressive action is due to the fact that, whilst being axially coupled to the support vanes which carry them, the friction facing members are axially movable relative to one another: in the inoperative state, that is to say in the absence of any load, they are axially separated from one another and under load they move towards one another, by virtue of elastic deformation of said support vanes.
In French Pat. No. 2,094,693, each of the support vanes is formed by a simple sheet metal member and to achieve the required progressive action this member is bent, that is to say when it is inoperative, with the friction facing members moved apart from one another, it features a circumferential succession of bends delimiting on it a circumferential series of bearing surfaces for one of said friction facing members alternating with bearing surfaces for the other of the latter.
In this case, the support vanes are always operative in compression, the friction facing members urging them towards a substantially plane configuration when, under load, they are caused to move towards one another.
In U.S. Pat. No. 2,256,698 each of the support vanes is also formed from a simple sheet metal member but, when inoperative, this is substantially plane and in order to achieve the required progressive action, the friction facing members feature recesses between the bearing areas adapted for bearing cooperation with said support vanes, axially recessed relative to said bearing areas.
In this case, the support vanes are always operative in traction, the friction facing members urging them towards a wave-like overall configuration when, under load, they are caused to move towards one another.
These arrangements have given and continue to give satisfaction.
However, for a given overall dimension in the axial direction, the progressiveness of engagement that they provide for is necessarily limited.
A general object of the present invention is an arrangement which, by combining the previous two arrangements, advantageously provides for increasing this progressiveness of engagement and also confers other advantages.